Various forms of hydrogenated nitrile rubbers have recently been introduced into the marketplace. Hydrogenated nitrile rubber has the advantage of being resistant to oxidative degradation at high temperature, as well as being resistant to corrosive environments such as acid environments. These materials have found utility in the manufacture of fan belts, seals, gaskets, and hoses in increasingly small and hot-running car engines.
One process for the production of hydrogenated polymers in latex form, particularly hydrogenated latex rubber, utilizes hydrazine and an unsaturated polymer as the starting materials. This process is more particularly described in U.S. Pat. No. 4,452,950, assigned to the Goodyear Tire and Rubber Company. However, the product produced in accordance with the process described in the '950 patent suffers from the disadvantage of containing residual unreacted hydrazine. This residual hydrazine is considered undesirable from an environmental and/or toxicity standpoint.
In view of the above, it would be highly desirable to provide a process for the elimination and/or reduction of the residual hydrazine in the hydrogenated polymer product mixture.
In one aspect, the present invention relates to a process for reducing or eliminating free hydrazine from a mixture of hydrazine and hydrogenated polymer, wherein said polymer is in latex form, which comprises contacting said free hydrazine in said mixture with a hydrazine scavanger in order to bind said free hydrazine, thereby reducing or eliminating the presence of free hydrazine in said latex.
In another aspect, the present invention relates to a two-step process for reducing or eliminating hydrazine from a mixture of hydrazine and hydrogenated polymer, said polymer being in latex form, which comprises:
(a) contacting said hydrazine in said mixture with a peroxide at a temperature of between about 30.degree. C. and about 60.degree. C., preferably between about 40.degree. C. and about 50.degree. C., in the presence of a metal ion initiator, in order to effect a reaction of said hydrazine with said peroxide in order to produce a purified mixture containing a reduced amount of hydrazine, and
(b) contacting said free hydrazine in said purified mixture with a hydrazine scavenger in order to bind at least a portion of said free hydrazine, thereby providing a desired mixture containing a reduced amount of free hydrazine.